Smoking and Tobacco Control Monograph No. 7 
which it is carried by particulate matter (tar droplets) deep into the lungs 
with inspired air. The nearly 2,000 °F microblast at the cigarette's tip is also 
the source of carbon monoxide and many other toxicologically significant 
pyrolysis products. Nicotine is rapidly absorbed in the alveoli of the lungs, 
concentrated in the pulmonary veins as a bolus, and pumped by the left 
ventricle of the heart throughout the body. Absorption characteristics are 
similar to those of gases, such as oxygen, that are exchanged in the lung 
from inspired air to venous blood (Henningfield et al., 1993). Thus, smoke 
inhalation produces arterial boli that may be 10 times more concentrated 
than the levels measured in venous blood (Henningfield et al., 1990 and 
1993). 
Psychoactive effects have rapid onset and short duration, dissipating 
within a few minutes. This short duration requires the user to self-administer 
the drug repeatedly, perhaps taking hundreds of puffs per day. The cigarette 
allows the smoker very fine, "fingertip," dose control. The powerful engulfing 
sensory effects are also important in dependence. It is not just the drug but 
the conditions and the cues that become associated with the drug that make 
nicotine dependence so tenacious. Finally, the cigarette is a convenient, 
portable system that permits easily repeated dosing. 
Benowitz (this volume) reviewed the pharmacokinetics of various 
nicotine delivery systems. Briefly, a cigarette produces a rapid spike of 
nicotine in the arterial blood. Smokeless tobacco products are also rapid, 
especially the higher pH tobacco products, and they require little practice 
for the user to achieve high nicotine levels. Whereas the nicotine dose 
obtained from a cigarette is largely determined by the behavior of the user, 
the nicotine dose obtained from a "chew" of smokeless tobacco is largely 
controlled by the product (Henningfield et al., 1995). In contrast to delivery 
from tobacco products, delivery of nicotine from polacrilex (nicotine gum) 
is slower and takes a great deal of practice and work to achieve even modest 
nicotine plasma levels. Transdermal nicotine medications (patches) provide 
slow absorption — so slow that users cannot reliably detect nicotine's effects. 
Fhe speed of delivery is clearly an important determinant of addictive effects, 
and the cigarette, like crack cocaine, provides an explosive dose of nicotine. 
NK^OTINE'.S Nicotine is a fascinating psychoactive drug. It was used to help map the 
EFFECT'S cholinergic nervous system early in the 20th century. Much of receptor 
theory and many of the methods used to study competitive agonists and 
antagonists were developed at the turn of the century using nicotine (Langley, 
1905). 
Nicotine has diverse effects, not only in the brain but also in the 
adrenals at)d skeletal muscles. I'hese diverse effects may ex{)lain why a 
smoker re[)orts that on some occasions cigarettes have relaxing effects and on 
other occasions, stimulating effects. Lhis has been referred to as a [raradoxical 
effect, but it is not paradoxical at all; other drugs generally referred to either 
as sedatives or stimulants also produce both sedating and stimulating effects 
((hhnan et al., 1990). Like tfie effects of these other drugs, nicotine's effects 
are conqrlicated; tliey de[)end on tfie dose, tfie time since dosing, how the 
